Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products

摘要

We assessed and evaluated the performance of five ocean reanalysis productsin reproducing essential hydrographic properties and their associatedtemporal variability for the Weddell Sea, Antarctica. The products used inthis assessment were ECMWF ORAS4 (European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4),CFSR (Climate Forecast System Reanalysis), MyOcean UR025.4 (University of Reading),ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and SODA (Simple Ocean Data Assimilation). Thepresent study focuses on the Weddell Sea deep layer, which is composed ofthe following three main water masses: Warm Deep Water (WDW), Weddell SeaDeep Water (WSDW) and Weddell Sea Bottom Water (WSBW). The MyOcean UR025.4product provided the most accurate representation of the structure andthermohaline properties of the Weddell Sea water masses when compared withobservations. All the ocean reanalysis products analyzed exhibited limitedcapabilities in representing the surface water masses in the Weddell Sea.The CFSR and ECCO2 products were not able to represent deep water masseswith a neutral density ≥ 28.40 kg m?3, which was considered theWSBW's upper limit throughout the simulation period. The expected WDW warmingwas only reproduced by the SODA product, whereas the ECCO2 product was ableto represent the trends in the WSDW's hydrographic properties. All theassessed ocean reanalyses were able to represent the decrease in the WSBW'sdensity, except the SODA product in the inner Weddell Sea.Improvements in parameterization may have as much impact on the reanalysesassessed as improvements in horizontal resolution primarily because theSouthern Ocean lacks in situ data, and the data that are currently available aresummer-biased. The choice of the reanalysis product should be madecarefully, taking into account the performance, the parameters of interest,and the type of physical processes to be evaluated.